JPH09150191A - Treatment of organic sewage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method which purifies sewage at a high speed, obviates the generation of excess sludge, eliminates the need for the incineration equipment to be exclusively used for sludge and obviates the elution of heavy metals from incineration ashes. SOLUTION: A flocculating agent 10 is added to the org. sewage of sewer 8, etc., to execute flocculation and sepn. 2. A separated liquid 12 is then subjected to the removal of soluble BOD-related component by a biological treating stage 3 using packed beds of aerobic immobilizing microorganisms. Ozone 16 is added to the excess sludge 14 of the biological treating stage 3 and the sludge is returned 15 to the fore stage of the flocculating and separating stage. The dehydrated cake 17 of the flocculated and separated sludge 11 is mixed with org. waste 18, such as municipal refuse and after the mixture is thermally cracked and gasified by a fluidized bed gasifying furnace 6, the flying ashes from the fluidized bed furnace 6 are melted and separated 7. The fluidized bed gasifying furnace 6 is utilized by supplying the grit 8 discharged from a sewage settling basin 1 as a fluid medium together with the dehydrated sludge and the waste, such as municipal refuse to the fluidized bed gasifying furnace.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for treating organic sewage, and more particularly to a method for rationally treating organic sewage such as sewage or human waste and waste such as municipal waste and various industrial wastes. Belong to

[0002]

2. Description of the Related Art Conventionally, sewage is biologically purified by an activated sludge method that requires a large installation area in a sewage treatment facility, and sewage sludge that is difficult to dehydrate is exclusively used in the sewage treatment facility. It is treated in the sludge dewatering equipment and incineration equipment. Therefore, a large amount of equipment cost and maintenance cost are required for the water treatment process and the sludge treatment process. In the case of human waste treatment, the exact same problem occurs. Furthermore, since sewage sludge incineration ash contains harmful heavy metals such as lead and mercury in a considerably high concentration, it is difficult to dispose of the ash. Further, since the sand discharged from the sewage settling basin is contaminated with organic substances such as human waste, conventionally, the sewage treatment water was used to thoroughly wash the sand before it was landfilled. However, sand cleaning is troublesome, and there is not enough land for disposal of sand after cleaning. It is also known that the sewage is biologically purified by a packed bed of granular filter media such as anthracite with aerobic microorganisms immobilized.
Therefore, it is not practical because there is a big problem that the filling layer is clogged very quickly.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, purifies sewage at high speed, can significantly reduce the required area of the biological treatment tank for sewage, and makes sludge treatment extremely difficult. Eliminates the generation of hard-to-dewater surplus sludge, eliminates the need for a dedicated incinerator for sludge in sewage treatment facilities and human waste treatment facilities, and prevents the elution of heavy metals from incinerated ash while cleaning the sediment. An object of the present invention is to provide a method for treating organic wastewater that makes it unnecessary to dispose of washed sand.

[0004]

In order to solve the above problems, in the present invention, a coagulant is added to an organic wastewater such as sewage for coagulation separation, and then the separated liquid is filled with aerobic immobilized microorganisms. Soluble BOD is removed by a biological treatment process using a bed, and the dehydrated cake of the coagulation-separation sludge is mixed with organic waste such as municipal waste, pyrolyzed and gasified by a fluidized bed gasification furnace, and then fluidized. Melts fly ash from the floor furnace
This is a method for treating organic sewage characterized by separation.

In the present invention, a coagulant is added to organic wastewater such as sewage to coagulate and separate, and then the separated liquid is subjected to a biological treatment process using a packed bed of aerobic immobilized microorganisms to obtain soluble BOD. After removing and adding ozone to the excess sludge of the biological treatment process and returning it to the previous stage of the coagulation separation process, the dehydrated cake of the coagulation separation sludge is mixed with organic waste such as municipal waste, and fluidized bed gasification This is a method for treating organic sewage, which is characterized by melting and separating fly ash from a fluidized bed furnace after pyrolysis and gasification in a furnace. In the above method, the fluidized bed gasification furnace can be used by supplying the sand discharged from the sand basin of the wastewater as a fluid medium to the fluidized bed gasification furnace together with the waste such as the dehydrated sludge and municipal waste. .

[0006]

Next, the present invention will be described in detail.
FIG. 1 is an overall process diagram showing the flow of the treatment method of the present invention, and the treatment method of the present invention for sewage will be described with reference to FIG. After the sewage 8 passes through the sand basin 1, a flocculant (inorganic and organic flocculant) 10 is added, and the flocculation flocs 11 are separated at high speed by the flocculation / separation device 2. As the coagulation / separation device 2, an upflow filtration tank filled with a buoyant hollow cylindrical filter medium, or a blanket type high speed granulation / sedimentation device is suitable. Suitable inorganic coagulants are aluminum sulphate, ferric chloride and polyiron sulphate. It is sufficient that the injection rate of the inorganic coagulant is about 200 to 400 mg / l.

As the polymer coagulant, a polyacrylamide type anionic polymer coagulant is suitable. In this coagulation-separation step 2, the sewage's SS BOD, SS, and phosphorus are highly (90
% Or more) is removed. When the filtration device using a hollow cylindrical filter medium is applied to the coagulation / separation device 2, the particle size of the filter medium is 10 to 40 mm, the packed bed thickness is 2 to 3 m, and the filtration speed is set to 100 to 300 m / d. Is good. When a high-speed granulation / precipitation device (trade name PBS-Ebara Co., Ltd.) is used, the separation speed is 500 to 1000 m /
It can be set to d.

Flocculant-separated water (SS
10 mg / l, BOD 30 mg / l, phosphorus 0.5 mg /
1, nitrogen 25 mg / l is the average water quality) 12 is a packed bed in which BOD-assimilating bacteria are immobilized on the surface of a granular filter medium such as anthracite, plastic particles, sponge, granular activated carbon, and granular zeolite (for example, trade name Bio Packed or Bio-Excel-Ebara Co., Ltd. product) flows into the immobilized microbial filter bed 3 to obtain clear treated water 13 from which BOD is removed by 90% or more at high speed. The particle size of the filter medium is 2-1
It is suitable that the thickness is 5 mm and the filling layer thickness is 1.5 to 2 m. Since the water flow rate to the packed bed can be set to a high value of 200 to 240 m / d, the sewage can be purified in a remarkably short time of about 20 minutes as the retention time. In the conventional activated sludge method, 7
A residence time of ~ 8 hours is required.

Since the SS is removed by the coagulation separation, the clogging of the packed bed is remarkably slow. However, if it is operated for a long time, the filtration resistance of the packed bed gradually increases due to the growth of microorganisms. The packed bed is washed once a day (sufficiently once a day), and the washing waste water 14 is discharged. Although the cleaning wastewater 14 contains microbial sludge, ozone 16 is added to the microbial sludge to solubilize the microbial sludge in the ozone oxidation tank 4, and the solubilized sludge 15 containing BOD is returned to the coagulation separation step 2. Then, the sludge that has not been solubilized is solid-liquid separated. The appropriate amount of ozone added is 20 to 30% based on the weight of microbial sludge SS, and the amount of ozone can highly solubilize biological sludge to about 80 to 90%. According to the present invention, since the hardly dehydratable surplus sludge is solubilized by ozone, there is a great effect that surplus biological sludge hardly occurs.

Therefore, the sludge supplied to the dehydration step 5 is
Substantially only agglomerated and separated sludge (greatly superior in dehydration property to surplus biological sludge) 11 of raw sludge can be dehydrated very effectively, and dehydration at a low pressure like a belt press type dehydrator. Even in the machine 5, a dehydrated cake with low water content (water content in the range of 60%) 17 can be easily obtained, and the heating value of the cake is improved, which leads to a reduction in fuel cost in the subsequent gasification / melting process. In addition, the sediment 9 is supplied to the gasification process 6 together with the dehydrated sludge 17, municipal waste 18, etc. without being washed,
Since contaminants adhering to the sand can be pyrolyzed, the conventional settling sand cleaning equipment becomes unnecessary. Gasification process 6
Uses a fluidized bed gasifier with sand as the fluid medium,
Sediment from sewage can be used as make-up sand for a fluidized bed reactor.

Next, the gasification / melting process will be described in detail with reference to FIG. The sewage sludge dewatering cake 17 and the settling sand 9 are supplied to a fluidized bed gasification furnace 6 together with wastes (biomass wastes, plastic wastes, automobile dismantling wastes-for example, shredder dusts) 18 such as municipal wastes for pyrolysis gasification. receive. The reaction temperature for gasification is 450-80
Set to a relatively low temperature range of 0 degrees. The raw materials that have fallen into the fluidized bed of the gasification furnace 6 are fluidized gas (air, oxygen-enriched air,
Upon contact with (selected from oxygen-steam mixture) 23, it is rapidly pyrolyzed and gasified. As a result, gas, tar, carbide, and steam are produced, but the carbide is crushed by the disturbing motion of the fluidized bed to form char. These 24 are collectively supplied to the primary combustion chamber of the post-stage swirl melting furnace 7, and are rapidly oxidized at a high temperature of 1300 ° C. or higher while being mixed with oxygen in the swirl flow. Therefore, the ash contained in the char becomes slag mist, is captured on the furnace wall by the centrifugal force of the swirling flow, flows down the furnace wall and enters the secondary combustion chamber, and is discharged as slag 19 from the furnace bottom of the slag separation section. To be done.

The oxidation reaction is completed in the secondary combustion chamber and becomes a gas 25 consisting of hydrogen, carbon monoxide, carbon dioxide and steam.
The gas 25 exiting the melting furnace 7 collects steam in the exhaust heat boiler 20, separates ash in the bag filter 21, and then cools and cleans it in the scrubber 22 using an aqueous sodium hydroxide solution to remove hydrogen sulfide in the gas. Are removed. In this way, the purified syngas 26 is obtained. This syngas 26 can be supplied to a gas turbine to generate electric power, and the electric power can be used as electric power for an aeration blower for biological treatment in a sewage treatment facility. Since the heavy metals in the sewage sludge are completely fixed in the molten slag, the problem of heavy metal re-elution to the environment can be fundamentally solved. Slag can be used as a material for civil engineering and construction such as roadbed material, aggregate, etc. In addition, harmful substances such as dioxins, furans, and PCBs in the waste are completely decomposed in the melting furnace at a high temperature of 1300 degrees.

[0013]

According to the present invention, the following effects can be obtained. (1) Sewage can be highly purified in a short period of time with a biological treatment device that is significantly space-saving, and phosphorus, nitrogen, SS,
Since highly treated water from which BOD is highly removed can be obtained,
Can innovate sewage treatment. In addition, the sludge incineration facility of the sewage treatment facility is no longer required, which can greatly streamline the process. (2) Surplus biological sludge, which is difficult to dehydrate and is extremely difficult to treat, is hardly generated. (3) Since only raw sludge with good dewatering property (coagulated separation sludge) needs to be dewatered, a low-moisture dehydrated cake can be easily obtained and mixed with various wastes such as municipal waste to be gasified for energy saving.・ Can be melted. (4) Since the settled sand can be used as the fluidized medium of the fluidized bed gasification furnace, cleaning and disposal of the settled sand becomes unnecessary. (5) Since the harmful heavy metals contained in the sewage sludge are firmly fixed in the molten slag of ash such as municipal waste, the biggest problem (heavy metal problem) in the disposal of the sewage sludge is solved. (6) Energy can be recovered from waste such as sewage sludge, human waste sludge, and municipal waste.

[Brief description of the drawings]

FIG. 1 is an overall process diagram showing a flow of a processing method of the present invention.

FIG. 2 is a partial process diagram showing a gasification / melting portion.

[Explanation of symbols]

1: sand basin, 2: flocculation and separation device, 3: immobilized microbial filter, 4: ozone oxidation tank, 5: dehydration device, 6: gasification furnace,
7: melting furnace, 8: sewage, 9: sand set, 10: coagulant, 1
1: Coagulated sludge, 12: Separated water, 13: Treated water, 14: Washing wastewater containing excess sludge, 15: Solubilized sludge, 16: Ozone, 17: Dewatered cake, 18: Waste such as municipal waste,
19: Molten slag, 20: Exhaust heat boiler, 21: Bag filter, 22: Scrubber, 23: Fluidized gas, 24:
Gas, tar, char, 25: gas, 26: syngas,

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C02F 11/10 C02F 11/10 Z

Claims (3)

[Claims] 1. A coagulant is added to an organic wastewater such as sewage to coagulate and separate, and the separated BOD is removed by a biological treatment process using a packed bed of aerobic immobilized microorganisms. The dehydrated cake of the coagulated separation sludge is mixed with organic waste such as municipal waste, pyrolyzed and gasified by a fluidized bed gasification furnace, and then fly ash from the fluidized bed furnace is melted.
A method for treating organic sewage, characterized by separation. 2. A coagulant is added to organic wastewater such as sewage for coagulation separation, and then the separated liquid is subjected to a biological treatment process using a packed bed of aerobic immobilized microorganisms to remove soluble BOD. While adding ozone to the excess sludge of the biological treatment process and returning it to the previous stage of the coagulation separation process, mixing the dehydrated cake of the coagulation separation sludge with organic waste such as municipal waste,
A method for treating organic sewage, which comprises melting and separating fly ash from a fluidized bed furnace after pyrolysis and gasification in a fluidized bed gasifier. 3. The fluidized bed gasification furnace, wherein the sand discharged from the sand basin of the wastewater as a fluid medium is supplied to the fluidized bed gasification furnace together with the waste such as the dehydrated sludge and municipal waste. The method for treating organic wastewater according to claim 1 or 2, characterized in that.